update windows build to Python 3.7

Lib/lib2to3/fixes/fix_set_literal.py

@@ -0,0 +1,53 @@
+"""
+Optional fixer to transform set() calls to set literals.
+"""
+
+# Author: Benjamin Peterson
+
+from lib2to3 import fixer_base, pytree
+from lib2to3.fixer_util import token, syms
+
+
+
+class FixSetLiteral(fixer_base.BaseFix):
+
+    BM_compatible = True
+    explicit = True
+
+    PATTERN = """power< 'set' trailer< '('
+                     (atom=atom< '[' (items=listmaker< any ((',' any)* [',']) >
+                                |
+                                single=any) ']' >
+                     |
+                     atom< '(' items=testlist_gexp< any ((',' any)* [',']) > ')' >
+                     )
+                     ')' > >
+              """
+
+    def transform(self, node, results):
+        single = results.get("single")
+        if single:
+            # Make a fake listmaker
+            fake = pytree.Node(syms.listmaker, [single.clone()])
+            single.replace(fake)
+            items = fake
+        else:
+            items = results["items"]
+
+        # Build the contents of the literal
+        literal = [pytree.Leaf(token.LBRACE, "{")]
+        literal.extend(n.clone() for n in items.children)
+        literal.append(pytree.Leaf(token.RBRACE, "}"))
+        # Set the prefix of the right brace to that of the ')' or ']'
+        literal[-1].prefix = items.next_sibling.prefix
+        maker = pytree.Node(syms.dictsetmaker, literal)
+        maker.prefix = node.prefix
+
+        # If the original was a one tuple, we need to remove the extra comma.
+        if len(maker.children) == 4:
+            n = maker.children[2]
+            n.remove()
+            maker.children[-1].prefix = n.prefix
+
+        # Finally, replace the set call with our shiny new literal.
+        return maker